Keysight 34465A vs Fluke 8846A vs others

[arijav]

Hello,

I am currently planning to buy a 6.5 digit DMM for a lab. We plan to use it to calibrate measurement systems (German DAkkS) where we need to go to accuracies in the order of 0.1mV for a voltage range of +/-10V. We need as well to calibrate thermocouple inputs. We have been using to calibrate our equipment in the past a Fluke 8846A which was sent yearly for an official DAkkS calibration. I need to buy a new unit and I am wondering about what would be the best option nowadays. Would you recommend the Keysight 34465A?, still a Fluke 8846A or something else?.

I understand both the Keysight as well as the Fluke use LM399 voltage references. For this price range there is none with LTZ1000 right?

Thanks

[bdunham7]

I am currently planning to buy a 6.5 digit DMM for a lab. We plan to use it to calibrate measurement systems (German DAkkS) where we need to go to accuracies in the order of 0.1mV for a voltage range of +/-10V. We have been using to calibrate our equipment in the past a Fluke 8846A which was sent yearly for an official DAkkS calibration. I need to buy a new unit and I am wondering about what would be the best option nowadays. Would you recommend the Keysight 34465A?, still a Fluke 8846A or something else?.

I understand both the Keysight as well as the Fluke use LM399 voltage references. For this price range there is none with LTZ1000 right?

The Fluke 8846A is discontinued, but Welectron may still have some stock.  What happened to yours? 

I think someone made a home-brew LTZ1000 setup for the Keysight 34465A, but in general just changing the reference doesn't help much.  An aged and selected LM399 is more than good enough for this type of meter and other issues (tempco of divider resistors, etc) will dominate the errors.

The Keithley DMM6500 is the designated replacement for the 8846A.

Your stated accuracy requirement of +/- 0.1mV @ 10V is 10ppm, a spec which is not specified by any 6.5-digit meter and is also beyond the specified capability of even 7.5 digit meters like the Keithley DMM7510 or Keysight 34470A.  Only 8.5 digit meters achieve <10ppm. Your 8846A may have been performing this well in actual practice (mine does, easily) but it isn't specified to, so I don't know how that affects your requirements. 

[arijav]

Thanks for your input, specially related to the need of a 8.5 digit one to reach the ppm. Up to now somehow it was working fine with the Fluke, so we will try to stay in 6.5 to keep the costs reasonable. Regarding the Fluke 8846A, it is still fine, the reason to acquire a new DMM is because we have now a second lab location and we wanted to have one there as well.

[bdunham7]

Up to now somehow it was working fine with the Fluke, so we will try to stay in 6.5 to keep the costs reasonable.

In that case I'd recommend you contact Welectron immediately to see if they still have the 8846A in stock and just buy it if they have it.  None of its competitors nor any available replacement quite match its accuracy and stability, in theory (specification) or in practice.